Richard,
As much as it pains me, I have to agree with syn08 on this one. (must be getting soft in the head).........
From what I gather to get a working CMA (for audio applications) you need a 1)buffer 2)gain amplifier 3)CMA (current conveyor) and 4)output stage (to handle complex loads).
The scary part is the complexity required to maintain bandwidth and distortion numbers which are academic at best and could hurt the sonic performance of the unit. So now we need four separate blocks to do what you can do in one or two, with the added complexity of dealing with stability issues of getting all these blocks to work together. Sounds like a solution in hunt of a problem.
Krell used this topology (or should I say ideology) in their Cast system and it was universally panned. It sounded flat and lifeless though it claimed low distortion and wide bandwidth.
Maybe you could publish a working circuit to prove me wrong and I will stand to be corrected.
Jam
Dear Jam, my old buddy,
It isnt complex at all. You can do it with 4 transistors if you want. I have no idea what you or krell tried so how can i say anything about it.
I will say it again.... make an amp which has constant BW with gain. and make it all in low Z values. and Ultra low THD.
Sorry, guys. You will have to figure how-to yourselves. Good luck.
Thx-RNMarsh
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I have the strong feeling that you didn't get the point that I made.
To my definition when related to audio, a servo should try to keep the output DC as close to zero as possible, independent of the input signal.
And that's exactly what your servo fails to do.
So X Volt DC in results in X Volt DC out, is that what you want ??
That's because your "servo" compares DC in the input signal to DC in the output signal and tries to keep them as close as possible, aka error correction within the BW of your LPF.
And no, there is absolutely no audio signal cancelled by the comparator, just and only error correction introduced by the PA.
A lot of unfounded assumptions, implying that further discussion won't probably bring anything at all, just like in so many other discussions
Hans
Perhaps, Waly, you dont consider HF from digital artifacts to be in the same BW as EMI?
Interesting view.
You are boring me, Waly.
-RNM
Regarding the listening test for accuracy.
First you do need a really good microphone... at least much better than your speakers. That is true. But, that isnt really so hard to find.
Regarding the room 'sound' pickup --- close mic'ed it is very much lower than the recorded voice and isnt a factor IMO... But let me explain more... I made it a point to use a person whom you know very well... like a spouse. You know that voice is thier voice no matter over a land line phone with poor s/n and high distortion and 300-3.5KHz BW. You can pick out that voice in a crowd of people. You can know it is that same person in a reverberant church or anechoic chamber. We have excellent pattern recognition skills.
When you hear that recorded voice played back, you know if it sounds real or not. And, to what degree it is like the familiar voice spoken live. If you wish, you can move loudspeaker to center where person was. Which is a good idea anyway to have a center speaker/channel IMO. But that is another subject.
THx-RNMarsh
First you do need a really good microphone... at least much better than your speakers. That is true. But, that isnt really so hard to find.
Regarding the room 'sound' pickup --- close mic'ed it is very much lower than the recorded voice and isnt a factor IMO... But let me explain more... I made it a point to use a person whom you know very well... like a spouse. You know that voice is thier voice no matter over a land line phone with poor s/n and high distortion and 300-3.5KHz BW. You can pick out that voice in a crowd of people. You can know it is that same person in a reverberant church or anechoic chamber. We have excellent pattern recognition skills.
When you hear that recorded voice played back, you know if it sounds real or not. And, to what degree it is like the familiar voice spoken live. If you wish, you can move loudspeaker to center where person was. Which is a good idea anyway to have a center speaker/channel IMO. But that is another subject.
THx-RNMarsh
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Give it a rest. No, you are the expert. Now go design a CMA power amp. That should keep you busy.
-RM
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I don't need to do that, in particular for free. You already have 5 EEs working for you, as a Project Manager, put them on the job.
Wow, as if cbdb is on your ignore list. Either that or your own belief is so strong that audio physics is not relevant in your test, compounded by your urge to sell your audio gear, your opinion becomes universal fact, in your own bubble.
What's up with this re Bangkok city planners (quoting the NYT)?
Looks like soon it will be just like home.
I heard that on an independent travel board a few weeks back. Guess there's no reason to go back after 30 odd years... probably no more Elvis impersonators in the recreational haunts (bars) either... and I need some more fake Rolex, Benetton, Hilfiger shirts, counterfeit Kentucky Fried Chicken .....whatever
next thing they'll be taking the fun out of sin
Hi Richard, good to have you back. I missed what happened earlier.
I mostly agree with you that CMA has some real advantages, but I still make some VFA amps when necessary, like my latest JC-1+ power amp that is on my test bench right now. Perhaps, now that you remind me, I should test its distortion at 100KHz or so.
I agree with you that digital circuitry seems to leak a lot of ultra high frequency, fast rise-time stuff, above and beyond normal audio signals. Your assertion that it IM's down is very creditable. I should look more into that.
I mostly agree with you that CMA has some real advantages, but I still make some VFA amps when necessary, like my latest JC-1+ power amp that is on my test bench right now. Perhaps, now that you remind me, I should test its distortion at 100KHz or so.
I agree with you that digital circuitry seems to leak a lot of ultra high frequency, fast rise-time stuff, above and beyond normal audio signals. Your assertion that it IM's down is very creditable. I should look more into that.
Make sure you have the right tools for this. Your SRS SR-1 analyzer has a maximum bandwidth of only 200KHz.
Sorry been busy with reality for a few days so not had a chance to answer this. Joe's view is that, because F=BIL therefore current drive is better for dynamic speakers. My clearly poor attempt at humour was that, because transformer flux is caused by current therefore an electrostatic speaker is a current device. In a world where complex numbers don't exist this seems logical
That seems like a tourist view of bangkok. There are a couple areas that tourist visit a lot. in those areas, they are 'cleaning' it up. Street vendors cause a lot of tourists to get sick... bad for economy. Thailand gets around 30 million tourist a year, so image and safety and comfort for them is important.
But, outside those hot spots, its business as usual. next to me is night time food vendors a plenty. And, far enough away from city center so that few speak English.
The gap between rich and poor is quit extreme though. Plenty of wealthy people here. swiss bank says there are 91,000 millionaires here and 324 billionares. They want their comfort too. Probably all living in bangkok. Minimum wage was increased recently to about $1.50/hr.
-Richard
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As far as I'm concerned they can place whatever they choose where the sun does not shine. The street food in Asia is for tourists that's about as clueless a comment as I have ever seen.
BTW the article had nothing to do with health issues. I guess the posh folks don't like to mix with the hoi poloi.
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